Methods and apparatus for controlling metals in liquids

ABSTRACT

Method and apparatus for controlling metals in a liquid are described. The liquid is contacted with a hexahydrotriazine and/or a hemiaminal material, and metal is adsorbed from the liquid onto the material. The hexahydrotriazine and/or hemiaminal material may be made from a diamine and an aldehyde.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of co-pending U.S. patent application Ser. No.14/305,625 filed Jun. 16, 2014, which is incorporated herein byreference.

BACKGROUND

The present disclosure relates to metal sequestration in fluids, andmore specifically, to use of hexahydrotriazine and hemiaminal molecules,oligomers, and polymers derived from aromatic, aliphatic, and/orpolyether diamines to sequester and/or remove metals from liquids.

Many commercially important processes exist to remove metals fromliquids. Metals are routinely removed from water for drinking, forpurification of groundwater, and for remediation of toxic sites. Metalsare also removed from other liquids, such as polar and non-polar organicliquids. Removing trace metals often requires costly additives andinstrumentation. There is a need in the art for a sensitivecost-effective way to remove trace metals from liquids.

SUMMARY

According to one embodiment of the present disclosure, a method includesexposing a liquid containing metal to a HA or HT metal control material;adsorbing metal from the liquid onto the metal control material; andremoving the metal from the liquid by separating the metal controlmaterial from the liquid. The metal control material may be a reactionproduct of an aldehyde and a primary diamine.

According to another embodiment, an apparatus includes a housing; ametal control material comprising an HA material or an HT materialdisposed in the housing; a connection structure coupled to the housing;and a support disposed in the housing and supporting the metal controlmaterial.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a UV spectrograph of a metal control material before andafter exposure to metal according to one embodiment.

FIG. 1B is a graph showing the effect of increasing lithium dose on UVabsorption absorption of a metal control material according to anotherembodiment.

FIG. 2 is a flow diagram summarizing a method of removing metals from aliquid according to one embodiment.

FIG. 3A is a schematic side-view of an apparatus for removing metals ina liquid according to another embodiment.

DETAILED DESCRIPTION

Hexahydrotriazine (HT) materials and hemiaminal (HA) materials derivedfrom aromatic, aliphatic, and/or polyether diamines may be used as ametal control material to sequester or remove metals from a liquid. Themetal control materials may be single molecule species, oligomers,and/or polymers (i.e., polyhexahydrotriazine, PHT, polyhemiaminal, PHA).The metal control materials may be made using an aromatic diamine, apolyether diamine, or a mixture thereof to react with a formaldehyde(i.e. formaldehyde or paraformaldehyde). Other methods of making suchmaterials include reacting amines with chloromethyl ether. Such metalcontrol materials will form a complex with metal ions in a liquid,partially or completely sequestering or removing the metal from theliquid to the metal control material. After loading with metal, themetal control material may be removed, or otherwise separated, from theliquid leaving a reduced metal content in the liquid. Possible metalwhich may be removed from the liquid may be, without limitation, silver,zinc, lithium, calcium, and europium.

FIG. 1A is a UV spectrograph of an exemplary metal control materialbefore and after exposure to metal ions according to one embodiment. TheUV absorption spectrum of the metal control material before exposure tometal ions is at 102, and the UV absorption spectrum of the samematerial after exposure to metal ions is at 104. FIG. 1A isrepresentative of the effect of various metals on various differentkinds of HT and HA materials. As metal dosing of the HT or HA materialincreases, UV absorption of the material changes, indicating metal isbeing sequestered from the liquid by the removal material. In theembodiment of FIG. 1A, the effect of exposing an HT material,1,3,5-triphenyl-1,3,5-triazinane, to a solution of lithiumtrifluoromethanesulfonate (also known as “triflate”) in 80%acetonitrile, with the balance dichloromethane, on the UV absorptionspectrum of the HT material is shown. FIG. 1B is a graph showing theeffect of increasing dosage of lithium in the mixture above. The data106 shows monotonically increasing absorption at a wavelength of 251.3nm with increasing metal dose, indicating increasing load of metal inthe removal material. A saturation effect with respect to metal dose isevident in FIG. 1B.

FIG. 2 is a flow diagram summarizing a method 200 of removing metal froma liquid according to another embodiment. The method 200 involves usinga nitrogen-containing organic material to sequester metals from a liquidand optionally remove the metals from the liquid. At 202, a fluidcontaining metal species is contacted with a nitrogen-containing organicmetal control material. The metal control material may include an HTmaterial or an HA material, or both. The metal control material may beany of the metal control materials described herein, single moleculespecies, oligomer species, and/or polymer species, and may be structuredaccording to any morphology convenient for making contact with theliquid. For example, the metal control material may be formed intoparticles, pellets, granules, powder, fibers, sheets, films, or anyother convenient form. The metal control material may also be supportedin any convenient way. For example, a sheet or film may be disposed on,or adhered to, a substrate, such as a pipe surface, plate, grid, mesh,sphere, fiber or fiber bundle, pellet, or particle. In another example,pellets, particles, granules, or powder may be disposed in a fixed orfluidized bed on a support that may be a perforated plate, mesh, stackedspheres, and the like. Any combination of the above may also be used.

Pellets, particles, granules, or powder forms may include particles of abase material coated with a metal control material. For example,particles of a structural polymer to which a metal control material willadhere may be coated with the metal control material. Structuralpolymers that may be used include polyolefins such as polyethylene andpolypropylene, polystyrene, polyurethane, polyisocyanurate, acrylicpolymers, polyesters, polyvinyl chloride, epoxy resins, polyamide,polyimide, fluoropolymer, and the like. The base material may be addedto the reaction mixture before forming the metal control material, andmay be present as the metal control material is formed in order toacquire a coating of the metal control material.

The liquid may be contacted with the metal control material in anyconvenient way. One way is to apply the liquid to a surface of a film ofthe metal control material. The film may be disposed on a support, suchas a platform or a rim, and the liquid may be flowed, poured, sprayed,spin applied, ribbon applied, or otherwise applied to the film. In someembodiments, the film may be coated onto, or even adhered onto, asubstrate. The metal control material may be immersed into the liquid,such as by dipping an article having a surface with the metal controlmaterial included therein into the liquid. The liquid may be flowed onor through the metal control material. The liquid may be sprayed on orthrough the metal control material. The liquid may be atomized into anaerosol that is contacted with the metal control material. The liquidmay penetrate the metal control material, if desired.

The liquid may contact the metal control material at a phase interface,which may be a solid-liquid interface or a liquid-liquid interface. Forexample, an organic phase containing an HA or HT material dissolved ordispersed therein may contact a metal-containing aqueous phase at aliquid-liquid interface where the HA or HT material may contact metalsin the aqueous liquid. In such an embodiment, the metal control materialmay be removed by decanting the organic phase, leaving an aqueous phasewith a reduced metal content.

For a heterogeneous phase process as described above, metal controleffectiveness may be improved by increasing the surface contact areabetween the two phases. In a solid-liquid system, particle size, surfacearea, and/or porosity may be adjusted to provide a desired contactsurface. If porosity is desired, a metal control material as describedherein may be foamed according to known procedures, and then the foammay be powdered or pulverized to form porous particles.

In another embodiment, the metal control material may be dispersed intothe liquid. The metal control material may be in a powder form, and maybe poured, or otherwise introduced, into the liquid. In some cases, themetal control material may be soluble in the liquid. If the metalcontrol material is insoluble, or not substantially soluble, in theliquid, the metal control material may be removed from the liquidfollowing an exposure period.

Without limitation to any specific mechanism, it is believed that metalscations (M^(+p)) in the liquid may associate with one or more nitrogenatoms in the metal control material to produce a complex according toformula (1):

wherein A⁻ is an anion. The metals are adsorbed onto the metal controlmaterial at a surface that contacts the liquid at 204. The surfaceremains in contact with the liquid for a residence time selected toallow a desired amount of adsorption to occur. Typically, a residencetime of 1 second to 60 minutes is used. The effective residence time maybe less than the actual residence time if a portion of the metal controlmaterial has reached saturation. If the available active surface of themetal control material is reduced, the actual residence time may beincreased to maintain an effective residence time within useful limits.In a continuous flow embodiment, the flow rate of liquid along, across,or through the metal control material may be slowed to increase theactual and effective residence time.

The liquid is separated from the metal control material at 206. Theseparation may be performed by removing the metal control material fromthe liquid, or by pouring the liquid out, in a batch process, or bystopping flow of the liquid and removing the metal control material in aflow process. It should be noted that multiple volumes or aliquots ofliquid may be contacted with the metal control material before the metalcontrol material is removed from service, although each individualaliquot or increment of flow is removed from contact with the metalcontrol material after a certain time.

The metal control material is typically contacted with liquid over anextended time and may be used for multiple volumes of liquid. After atime, the metal control material may become saturated with metal, andmay then exhibit reduced effectiveness. At 208, the metal controlmaterial may be regenerated to remove metal loading and restore themetal control effectiveness of the material. The metal control materialmay be contacted with a regeneration material, such as a basic liquid,to remove the metal. An exemplary basic liquid that may be used toregenerate the metal control material is a 1M aqueous solution of NaOH.Alternately, an aqueous solution of a strong acid may also be used toregenerate the metal control material. An acid solution having pH lessthan about 3 will disassemble and dissolve an HT or HA material, so anHA or HT material loaded with metal may be exposed to such a solution toremove the metal and some of the HA or HT material, leaving a cleanedsurface of HA or HT material.

An HT material suitable for forming a film for detecting metals asdescribed herein is a molecule, oligomer, or polymer that has aplurality of trivalent hexahydrotriazine groups having the structure

and

a plurality of divalent bridging groups of formula (2):

wherein L′ is a divalent linking group selected from the groupconsisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein R′ comprises at least 1 carbon and R″comprises at least one carbon, each starred bond of a givenhexahydrotriazine group is covalently linked to a respective one of thedivalent bridging groups, and each starred bond of a given bridginggroup is linked to a respective one of the hexahydrotriazine groups. Inone embodiment, R′ and R″ are independently selected from the groupconsisting of methyl, ethyl, propyl, isopropyl, phenyl, and combinationsthereof. Other L′ groups include methylene (*—CH₂—*), isopropylidenyl(*—C(Me)₂-*), and fluorenylidenyl:

For PHT materials with bridging groups of formula (2), the PHT may berepresented by formula (3):

wherein L′ is a divalent linking group selected from the groupconsisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein R′ and R″ independently comprise at least1 carbon. Each nitrogen having two starred wavy bonds in formula (3) isa portion of a different hexahydrotriazine group.

The PHT may also be represented by the notation of formula (4):

wherein x′ is moles, L′ is a divalent linking group selected from thegroup consisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein R′ comprises at least 1 carbon and R″comprises at least one carbon. Each starred bond of a givenhexahydrotriazine group of formula (4) is covalently linked to arespective one of the bridging groups. Additionally, each starred bondof a given bridging group of formula (2) is covalently linked to arespective one of the hexahydrotriazine groups. Polymer molecules may becapped or terminated by a capping group in place of a bridging group informulas (3) and (4). Examples of capping groups include CH₃, hydrogenatoms, ether groups, thioether groups, and dimethyl amino groups.

The PHT or HT can be bound non-covalently to water and/or a solvent(e.g., by hydrogen bonds).

Exemplary non-limiting divalent bridging groups include:

and combinations thereof.

A suitable PHT material may be made by forming a first mixturecomprising i) one or more monomers comprising two aromatic primary aminegroups, ii) an optional diluent monomer comprising one aromatic primaryamine group, iii) paraformaldehyde, formaldehyde, and/or anothersuitable aldehyde, and iv) a solvent, and heating the first mixture at atemperature of about 50° C. to about 300° C., preferably about 165° C.to about 280° C., thereby forming a second mixture comprising apolyhexahydrotriazine. The heating time at any of the above temperaturescan be for about 1 minute to about 24 hours. Diamine monomers suitablefor making such PHT materials may have the general structureH₂N—Ar-L′-Ar—N—H₂, where Ar denotes a benzene ring group and L′ isdefined as described above. Diluent monomers suitable for including inthe reaction are typically primary monoamines RNH₂, where the group Rbonded to nitrogen has a structure according to formula (5), formula(6), formula (7), and/or formula (8):

wherein W′ is a monovalent radical selected from the group consisting of*—N(R¹)(R²), *—OR³, —SR⁴, wherein R¹, R², R³, and R⁴ are independentmonovalent radicals comprising at least 1 carbon. The starred bonds informulas (5), (6), (7), and (8) denote bonds with the nitrogen atom ofthe primary amine monomer. Non-limiting exemplary diluent groupsinclude:

Diluent groups can be used singularly or in combination.

Non-limiting exemplary monomers comprising two primary aromatic aminegroups include 4,4′-oxydianiline (ODA), 4,4′-methylenedianiline (MDA),fluorenylidene)dianiline (FDA), p-phenylenediamine (PD),1,5-diaminonaphthalene (15DAN), 1,4-diaminonaphthalene (14DAN), andbenzidene, which have the following structures:

Non-limiting exemplary diluent monomers includeN,N-dimethyl-p-phenylenediamine (DPD), p-methoxyaniline (MOA),p-(methylthio)aniline (MTA), N,N-dimethyl-1,5-diaminonaphthalene(15DMN), N,N-dimethyl-1,4-diaminonaphthalene (14DMN), andN,N-dimethylbenzidene (DMB), which have the following structures:

HT and HA metal control materials may be used to sequester or removemetals without first forming a film. Small molecules, oligomers, andgels of metal control materials may be added to a liquid to expose themetal control material to the liquid, and the metal control material andany adsorbed metal may then be removed from the liquid. In some cases,the metal control material may also be analyzed for UV absorption todetect a saturation point. If the material is saturated with metal, aregeneration process may be performed, as described above in connectionwith FIG. 2. Some of the metal control materials described above may bereadily made into films. If a non-film material is used, other kinds ofdivalent bridging groups may be used to make the metal control material.It should be noted that many diamines will react with aldehydes such asformaldehyde to form metal control materials. Other exemplary diaminesinclude polyetherdiamines such as polyethylene glycol diamine. Alkyldiamines such as hexane diamine will also react with formaldehyde toform metal control materials. The polyether and alkyl derived materialsmight not readily form films, but gels, oligomers, and small moleculesmay be formed that are usable as metal control materials.

Metal control may be performed in a continuous-flow mode, a batch mode,or a combination thereof. In the continuous-flow mode, a body of HT orHA metal control material may be exposed to a continuous flow of liquidto allow metals from the liquid to be adsorbed by the metal controlmaterial. A UV absorption analyzer may be disposed to detect metalloading of the metal control material, if desired. In a batch mode, abody of HT or HA metal control material, optionally disposed on asupport, may be brought to a liquid to be processed and introduceddirectly in the liquid. Alternately, a fixed volume of the liquid may beintroduced to the metal control material, for example by adding theliquid to a vessel containing the metal control material.

FIG. 3A is a schematic side view of an apparatus 300 for controllingmetals in a liquid according to one embodiment. The apparatus 300 has abody 302 containing metal control material disposed in a housing 304.The housing 304 has a connection structure 306 for connecting theapparatus 300 to a source of liquid having metals to be controlled. Theconnection structure 306 may be a fitting or flange for connecting to aflow structure such as a pipe, tube, or other conduit. The housing 304may have any convenient cross-sectional shape, such as circular,rectangular, or square.

The body 302 includes one or more of the metal control materialsdescribed herein, and may take the form of a powder, a film orcollection of films, a fiber or collection of fibers, or a porous mass.In every form, the body 302 comprises one or more surfaces that has ametal control material for contacting a liquid.

The body 302 may be disposed on or in a support 308. For example, apowdered material may be supported on a perforated plate, mesh, sponge,or collection of spheres. A fiber material may be disposed linearlyalong a major axis of the apparatus 300, and may be terminated in asupport plate or mass. In a collection of fibers, the fibers may allhave the same length or a wide variety of lengths. The fibers may beparallel or non-parallel, and in an embodiment wherein the fibers areparallel and similar in length, the fibers may be curved or twisted, ifdesired, to provide a tortuous liquid flow path through the fibers.

In an embodiment wherein the metal control material is a powder, one ormore flow structures 310 may be included intermittently within the bodyto prevent fluid channeling through the powder. The flow structures 310may take the form of plates, meshes, or baffles that force fluid to flowalong a non-linear path through the apparatus 300. As shown in FIG. 3A,the flow structures 310 may be oriented axially, that is along the majoraxis of the apparatus 300, transverse to the major axis, or at anydesired angle between. The flow structures 310 may be flat or curved,and may be twisted to produce a rotating flow, such as a vortex flow,through the apparatus 300 to increase contact between the flowing liquidand the metal control material of the body 302. In one embodiment, flowstructures may be arranged in an alternating interleaved pattern toprovide a flow path through the body 302 that is parallel to a support308 in a first direction through the body 302 to a wall of the housing304, turns along the wall of the housing 304, and then parallel to thesupport 308 in a second direction opposite to the first directionthrough the body 302, for example in a boustrophedonic pattern.

The housing 304, connection structures 306, supports 308, and flowstructures 310 may each be a structurally strong material such as metalor plastic, or combinations thereof. Any of the housing 304, connectionstructures 306, supports 308, and flow structures 310 may be lined orcoated with a material, for example a fluoropolymer such as Teflon, toimprove flow and/or reduce adhesion of material to structures of theapparatus 300.

The apparatus 300 may be used in a staged metal control configuration.Metal control may be performed in stages using a plurality of metalcontrol modules such as the apparatus 300 in order to improve overallmetal control results. A first stage may remove a first portion of themetal in a liquid, and a second stage may remove a second portion of themetal in the liquid. Any number of stages may be used, and piping may beprovided to connect or bypass any particular stage, for example to allowthe stage to be replaced if saturation is reached. In some embodiments,a recycle flow may be provided to perform multiple passes of the liquidthrough one or more stages.

Metal control materials described above may be soluble to some extent inthe liquid being analyzed. The metal control materials may additionallybe functionalized to affect solubility in various liquids. For example,a bridging group L′ that has hydroxyl groups may be used to increaseaqueous solubility or affinity. Alternately, or additionally,substituents of the aromatic rings in the diamine or monoamine reactantsmay include hydroxyl groups to increase aqueous solubility or affinity.Likewise, hydrocarbon bridging groups L′ will tend to increasesolubility or affinity for hydrocarbon liquids.

A related material that may be used to detect metals in liquids is ahemiaminal (HA) material. A polyhemiaminal (PHA) is a crosslinkedpolymer comprising i) a plurality of trivalent hemiaminal groups offormula (9):

covalently linked to ii) a plurality of bridging groups of formula (10):

K′*)_(y′)  (10),

wherein y′ is 2 or 3, and K′ is a divalent or trivalent radicalcomprising at least one 6-carbon aromatic ring. In formulas (9) and(10), starred bonds represent attachment points to other portions of thechemical structure. Each starred bond of a given hemiaminal group iscovalently linked to a respective one of the bridging groups.Additionally, each starred bond of a given bridging group is covalentlylinked to a respective one of the hemiaminal groups.

As an example, a polyhemiaminal can be represented by formula (11):

In this instance, each K′ is a trivalent radical (y′=3) comprising atleast one 6-carbon aromatic ring. It should be understood that eachnitrogen having two starred wavy bonds in formula (11) is a portion of adifferent hemiaminal group.

The structure of formula (11) can also be represented using the notationof formula (12):

wherein x′ is moles and each bridging group K′ is a trivalent radical(y′=3 in formula (10)) comprising at least one 6-carbon aromatic ring.It should be understood that each starred nitrogen bond of a givenhemiaminal group of formula (12) is covalently linked to a respectiveone of the bridging groups K′. Additionally, each starred bond of agiven bridging group K′ of formula (12) is covalently linked to arespective one of the hemiaminal groups.

Non-limiting exemplary trivalent bridging groups for HA materialsinclude:

The bridging groups can be used singularly or in combination.

Polyhemiaminals composed of divalent bridging groups K′ can berepresented herein by formula (13):

wherein K′ is a divalent radical (y′=2 in formula (10)) comprising atleast one 6-carbon aromatic ring. Each nitrogen having two starred wavybonds in formula (13) is a portion of a different hemiaminal group.

More specific divalent bridging groups have the formula (14):

wherein L′ is a divalent linking group selected from the groupconsisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein R′ and R″ independently comprise at least1 carbon. In an embodiment, R′ and R″ are independently selected fromthe group consisting of methyl, ethyl, propyl, isopropyl, phenyl, andcombinations thereof. Other L′ groups include methylene (*—CH₂—*),isopropylidenyl (*—C(Me)₂-*), and fluorenylidenyl:

Polyhemiaminals composed of divalent bridging groups of formula (14) canbe represented herein by formula (15):

wherein L′ is a divalent linking group selected from the groupconsisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein R′ and R″ independently comprise at least1 carbon. Each nitrogen having two starred wavy bonds in formula (15) isa portion of a different hemiaminal group.

The polyhemiaminal of formula (15) can also be represented by thenotation of formula (16):

wherein x′ is moles, and L′ is a divalent linking group selected fromthe group consisting of *—O—*, *—S—*, *—N(R′)—*, *—N(H)—*, *—R″—*, andcombinations thereof, wherein R′ and R″ independently comprise at least1 carbon. Each starred nitrogen bond of a given hemiaminal group offormula (16) is covalently linked to a respective one of the bridginggroups. Additionally, each starred bond of a given bridging group offormula (16) is covalently linked to a respective one of the hemiaminalgroups.

The hemiaminal groups can be bound non-covalently to water and/or asolvent. A non-limiting example is a hemiaminal group that is hydrogenbonded to two water molecules as shown in formula (17):

In some embodiments, a hemiaminal material may form a covalent networkwith water molecules that may be a polyhemiaminal hydrate (PHH). A PHAmaterial of this form may be made, for example, by reaction ofpolyethylene glycol oligomers with paraformaldehyde. Such materials maybe organogels in some cases.

Typical HT and HA polymers and oligomers, and PHH materials, asdescribed herein may be disassembled in aqueous solutions. HT oligomersand polymers will disassemble into monomers and may dissolve in acidsolutions having pH less than about 3, such as less than about 2.5, forexample less than about 2. PHH materials may disassemble into monomersin neutral water. Such properties may be useful in regeneration of metalcontrol material that has been saturated with metal due to use over anextended period of time. The metal control material may be washed with asolution of appropriate pH to remove any portion of the metal controlmaterial saturated with metals and expose portions with lower, or zero,metal loading, thus regenerating the metal control material. Inembodiments with a removable detection element, a used detection elementmay be replaced with a new detection element, and the used detectionelement may be subjected to a regeneration process including exposure toan aqueous wash solution of appropriate pH. Alternately, metals may beremoved from the metal control materials described herein by exposure toa basic solution.

An HA material suitable for use according to the methods describedherein may be made using the same groups of reactants as for the HTmaterials. The diluent monomers described above may also be used to makeHA materials. A method of preparing a polyhemiaminal (PHA) comprisingdivalent bridging groups comprises forming a first mixture comprising i)a monomer comprising two or more primary aromatic amine groups, ii) anoptional diluent monomer comprising one aromatic primary amine group,iii) paraformaldehyde, and iv) a solvent. The first mixture is thenpreferably heated at a temperature of about 20° C. to about 120° C. forabout 1 minute to about 24 hours, thereby forming a second mixturecomprising the PHA. In an embodiment, the monomer comprises two primaryaromatic amine groups. The mole ratio of paraformaldehyde:total moles ofprimary aromatic amine groups (e.g., diamine monomer plus optionalmonoamine monomer) may be about 1:1 to about 1.25:1, based on one moleor equivalent of paraformaldehyde equal to 30 grams. The solvent can beany suitable solvent. Exemplary solvents include dipolar aproticsolvents such as, for example, N-methyl-2-pyrrolidone (NMP),dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF),N,N-dimethylacetamide (DMA), Propylene carbonate (PC), and propyleneglycol methyl ether acetate (PGMEA).

A PHT material may be prepared from a PHA material. The PHT can beprepared by heating a solution comprising the PHA at a temperature of atleast 150° C., such as about 165° C. to about 280° C. or about 180° C.to about 220° C., for example at about 200° C. for about 1 minute toabout 24 hours. Additionally, a mixed PHA/PHT copolymer may be made bypartially converting a PHA material to a PHT material. A combination oflow conversion temperature, for example about 150° C. to about 165° C.,and short conversion time, for example about 1 minute to about 10minutes, may be used to make a mixed PHA/PHT material.

An exemplary PHA material may be made by reaction of 4,4′-oxydianiline(ODA) with paraformaldehyde (PF). The product is a powder or solidplastic.

4,4′-Oxydianiline (ODA, 0.20 g, 1.0 mmol) and paraformaldehyde (PF, 0.15g, 5.0 mmol, 5 equivalents (eq.)) were weighed out into a 2-Dram vialinside a N₂-filled glovebox. N-methylpyrrolidone (NMP, 6.2 g, 6.0 mL,0.17 M) was added. The vial was capped but not sealed. The reactionmixture was removed from the glovebox, and heated in an oil bath at 50°C. for 24 hours (after approximately 0.75 hours, the polymer begins toprecipitate). The polyhemiaminal P-1 was precipitated in acetone orwater, filtered and collected to yield 0.22 g, >98% yield as a whitesolid.

A second exemplary PHA material may be prepared by reaction of4,4′-methylenedianiline (MDA) with PF:

ODA was substituted with 4,4′-methylenedianiline (MDA) and a mole ratioof MDA to PF of 1:5 was used. Solid yield of 0.15 g, 69%, was anamorphous, insoluble off-white powder.

A PHT material may be prepared by reaction of ODA and PF, as follows:

P-4, a polyhexahydrotriazine, was prepared by reaction of4,4′-oxydianiline (ODA) with paraformaldehyde (PF). ODA (0.20 g, 1.0mmol) and PF (0.15 g, 5.0 mmol, 2.5 eq.) were weighed out into a 2-Dramvial inside a N₂-filled glovebox. NMP (6.2 g, 6.0 mL, 0.17 M) was added.The reaction mixture was removed from the glovebox, and heated in an oilbath at 200° C. for 3 hours (after approximately 0.25 hours, the polymerbegins to gel in the NMP). The solution was allowed to cool to roomtemperature and the polymer was precipitated in 40 mL of acetone,allowed to soak for 12 hours, then filtered and dried in a vacuum ovenovernight and collected to yield 0.21 g, 95% yield of P-4 as anoff-white solid.

The metal control materials described herein may be included in acomposite material that may be used as a metal control material in anyof the embodiments described herein. Any desired blend material for acomposite may be added to the reaction mixture of diamine and aldehydeprior to formation of a reaction product. For example, reactants may bemixed at a non-reacting temperature, for example less than about 50° C.for some embodiments, and a solid polymer material, for example apowder, a fiber aggregate, or a nanotube aggregate, may be added. Theresulting combination may be mixed as the temperature is increased toform a reaction product. Any desired polymer may form a compositematerial with an HA, HT, or PHH material to provide selected properties.Carbon nanotubes may form a composite with HA, HT, or PHH materials.Polyolefin polymers may also form composite materials with a HA, HT, orPHH material. Such composite materials may be used as metal controlmaterials for sequestering or removing metals from liquids in someembodiments.

While the foregoing is directed to example embodiments of the presentdisclosure, other and further embodiments may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. An apparatus, comprising: a housing; a metalcontrol material comprising a PHA material disposed in the housing; aconnection structure coupled to the housing; and a support disposed inthe housing and supporting the metal control material.
 2. The apparatusof claim 1, further comprising a source of liquid fluidly coupled to theconnection structure.
 3. The apparatus of claim 1, further comprising aflow structure disposed within the metal control material.
 4. Theapparatus of claim 1, wherein the metal control material is a reactionproduct of an aldehyde and a primary diamine.
 5. The apparatus of claim4, wherein the PHA material comprises an aromatic bridging group.
 6. Theapparatus of claim 1, wherein the PHA material has a plurality oftrivalent hemiaminal groups having the structure

covalently linked to a plurality of bridging groups having the structureK′*)_(y′), wherein y′ is 2 or 3, and K′ is a divalent or trivalentradical comprising at least one 6-carbon aromatic ring.
 7. The apparatusof claim 6, wherein K′ is

wherein L′ is a divalent linking group.
 8. The apparatus of claim 7,wherein L′ is selected from the group consisting of *—O—*, *—S—*,*—N(R′)—*, *—N(H)—*, *—R″—*, and combinations thereof, wherein R′ and R″independently comprise at least 1 carbon.
 9. The apparatus of claim 8,wherein R′ and R″ are independently selected from the group consistingof methyl, ethyl, propyl, isopropyl, phenyl, and combinations thereof.10. An apparatus, comprising: a housing; a flow structure within thehousing; a connection structure coupled to the housing; a metal controlmaterial disposed in the housing, the metal control material comprisinga PHA material with a plurality of trivalent hemiaminal groups havingthe structure

covalently linked to a plurality of bridging groups having the structureK′*)_(y′), wherein y′ is 2 or 3, and K′ is a divalent or trivalentradical comprising at least one 6-carbon aromatic ring; and a supportdisposed in the housing and supporting the metal control material. 11.The apparatus of claim 10, further comprising a source of liquid fluidlycoupled to the connection structure.
 12. The apparatus of claim 10,further comprising a flow structure disposed within the metal controlmaterial.
 13. The apparatus of claim 10, wherein the metal controlmaterial is a reaction product of an aldehyde and a primary diamine. 14.The apparatus of claim 13, wherein the PHA material comprises anaromatic bridging group.
 15. The apparatus of claim 10, wherein K′ is

wherein L′ is a divalent linking group.
 16. The apparatus of claim 15,wherein L′ is selected from the group consisting of *—O—*, *—S—*,*—N(R′)—*, *—N(H)—*, *—R″—*, and combinations thereof, wherein R′ and R″independently comprise at least 1 carbon.
 17. The apparatus of claim 16,wherein R′ and R″ are independently selected from the group consistingof methyl, ethyl, propyl, isopropyl, phenyl, and combinations thereof.18. The apparatus of claim 10, where in the connection structure is aflange.
 19. An apparatus, comprising: a housing; a flow structure withinthe housing; a connection structure coupled to the housing; a metalcontrol material disposed in the flow structure, the metal controlmaterial comprising a PHA material with a plurality of trivalenthemiaminal groups having the structure

covalently linked to a plurality of bridging groups having the structureK′*)_(y′), wherein y′ is 2 or 3, and K′ is

wherein L′ is a divalent linking group; and a support disposed in thehousing and supporting the metal control material.
 20. The apparatus ofclaim 19, wherein the flow structure is arranged in an alternatinginterleaved pattern.